1. Field of the Invention
The invention relates to a handpiece as part of a treatment instrument or processing instrument or as part of a treatment device or processing device for medical purposes.
Such a handpiece may be, inter alia, a medical or dental treatment instrument or a processing instrument for a medical or dental laboratory.
2. Description of the Related Art
Medical or dental handpieces or treatment instruments differ, inter alia, by virtue of the function of the tool borne by them in each instance and by the operation of the drive. A tool may be driven by rotation, as is the case with a drill for example, or by an axial reciprocating movement, as is the case with a file, or also by a combination of these movements. A handpiece with a tool that is driven in rotation may also be used, given appropriate design of the tool, for the purpose of transmitting a rotary drive force to rotating parts, for example for tightening or loosening screws that are present at the treatment site, as is the case, for example, with screws pertaining to false teeth or to other parts of the body.
The use of an existing handpiece is problematic for several reasons. One problem is that, by reason of the rod-shaped design of the handpiece, in the event of a pivoting movement about the axis of the tool it is possible to exert a considerable leverage with it which, with regard to loading, both of the tool and of the tooth, can result in overstressing, for example it can result in the tool snapping or in the tooth being stressed so much as to be levered out. The existing problem arises in particular when the tool is one that serves to prepare a cavity in which the tool can snap, above all when the cross-sectional size of the tool is relatively small, as is the case with a treatment and processing tool for preparing a root canal of a tooth. If such a tool breaks in the course of the treatment it becomes lodged relatively firmly in the cavity accommodating it and in most cases cannot be removed. Possibilities to be reckoned with are that a snapped root-canal tool will impair the function of the tooth and the useful life thereof or may trigger a focus of inflammation resulting in premature loss of the tooth.
The problems described above arise in particular in the case of a handpiece with a root-canal tool because such a tool easily breaks by reason of its relatively small cross-sectional size and length and a fragment gets jammed in the root canal and, in most cases, cannot be extracted.
With such a handpiece, in which the tool performs a rotary-drive function, problems resulting from an overload may likewise arise, for example when a screw thread that serves to attach a tooth or a part of the body is overwound.